This invention relates to a liquid crystal layer alignment (orientation) method, and more particularly, to a method for obtaining a defectless aligned layer of a liquid crystal medium for liquid crystal device such as displays.
Great interest has focused recently to displays, memories or the like embodying ferroelectric liquid crystal mediums, which afford high device performances such as a quick response, an excellent property as a memory medium.
However, since the tendency to be crystallographically aligned is very strong in a ferroelectric liquid crystal, e.g., of smectic C*, smectic H* or the like as compared with such as in a nematic liquid crystal, creation of defects in an aligned liquid crystal is likely when prepared only by a horizontal alignment treatment, resulting in making some pixels unstable and the contrast low. Accordingly, It is necessary to produce stable domains in a ferroelectric liquid crystal layer to devise reliable display and memory.
For orientating a ferroelectric liquid crystal, there are known temperature gradiating methods making use of a spacer edge, a magnetic alignment methods, shearing methods, inclined deposition methods, rubbing methods and so forth. While each method has its advantage and its shortcoming, rubbing methods, which have been broadly used in production of TN liquid crystal devices, seem suitable for mass-production. In accordance with thus method, a uniform organic or inorganic film is formed on an inside surface of a substrate, and rubbed with a cloth in one direction, on which the director of liquid crytal molecules are aligned in the direction.
However, when aligned by a rubbing method, some defects may occur in the liquid crystal, i.e., zig-zag dislocations, making the vicinity unstable. The defects have been found as causes to make unclear the threshold voltage with respect to the response of the liquid crystal and to degrade the contrast of the liquid crystal device.